I have installed Microsoft.AspNet.WebApi.Cors package using Install-Package Microsoft.AspNet.WebApi.Cors in my WebApi project(.net framework 4.5.2)
Microsoft.AspNet.WebApi.Cors
Install-Package Microsoft.AspNet.WebApi.Cors
You need to install following nuget package for this.
Install-Package Microsoft.AspNet.WebApi.Cors.ko -Version 5.0.0
This will work.